Hi All,

I need to get the cached response fetched time from origin server which is
returned in the BE response with Date header. When I debugged the
cache-mediator code, I found that when caching the response Date header is
added to the cache. But when I retrieve the cached response for the
subsequent request, Date header is removed from the cached response.

This is due to we are removing the Date header from the response [1] and
send a new Date header with the response to the user. If we set the
preserveHeaders(in passthru-http.properties), I was able to get the Date
header from the cached response as well.

So, as I need the response fetched time to calculate the TTL value of the
cached response, I am planning to add a property to the cached response to
store the fetched time and use it to calculate the TTL. Or do we need to
suggest the user to set the preserve header?


[1].
https://github.com/wso2/wso2-synapse/blob/master/modules/transports/core/nhttp/src/main/java/org/apache/synapse/transport/passthru/util/PassThroughTransportUtils.java#L160

Thanks,
Keerthika.

On Tue, Jan 23, 2018 at 8:26 PM, Keerthika Mahendralingam <
[email protected]> wrote:

> Hi All,
>
> I am trying to add an Age header when returning the cached response(as
> discussed in [1]). I am following the steps as follows:
>
>    - If the response doesn't have the Date header, add Date header (with
>    current time) when caching the response[2].
>    - For the subsequent request, get the Date header value of the cached
>    response, timeout and current requested time and find the TTL value as:
>
> TTL = difference ((DateHeaderValue + timeout), CurrentTime)
>
>
>    - Set the TTL value as Age header.
>
> Please let me know if you have any concerns on this.
>
> [1]. [Architecture][RRT] Improving caching based on cache-control and ETag
> headers
> [2]. https://tools.ietf.org/html/rfc2616#page-124
>
> Thanks,
> Keerthika.
> --
> <[email protected]>
> Keerthika Mahendralingam
> Software Engineer
> Mobile :+94 (0) 776 121144 <+94%2077%20612%201144>
> [email protected]
> WSO2, Inc.
> lean . enterprise . middleware
>



-- 
<[email protected]>
Keerthika Mahendralingam
Software Engineer
Mobile :+94 (0) 776 121144
[email protected]
WSO2, Inc.
lean . enterprise . middleware
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